Effect of dexamethasone on TSH secretion induced by TRH in human obesity.

BACKGROUND: The presence of an abnormally high thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) makes it difficult to distinguish some euthyroid obese subjects from subelinically hypothyroid obese patients. Here, we examine whether such distinction may be achieved after treatment with glucocorticoids, which inhibit TSH secretion at the hypothalamic-pituitary level. METHODS: TRH tests (200 microg as an intravenous bolus injection) were performed in 30 age- and weight-matched, obese, but otherwise healthy, men. All subjects were tested again with TRH after treatment with dexamethasone (dex) (2 mg/d in four divided doses orally for 3 days). RESULTS: In all subjects, total thyroxine and triiodothyronine concentrations were in the normal range. According to basal and TRH-stimulated serum thyrotropin (TSH) levels, subjects were divided into the following three groups: group I (n=10), euthyroid subjects; group II (n=10), euthyroid subjects with normal basal but abnormally elevated TSH responses to TRH; group III (n=10), subjects with elevated basal and TRH-induced TSH levels (subclinical hypothyroidism). Basal TSH levels were 1.8+/-0.4 mU/L in group I, 1.7+/-0.3 in group II, and 6.0+/-0.7 in group III. In both groups II and III, TRH-induced TSH increments were above the normal range (maximal increment> 15 mU/L) and were significantly higher than in group I. After the second treatment with TRH, pretreatment with dex significantly decreased both basal TSH levels and peak TSH responses to TRH in all groups. However, a striking percentage decrease (>50%) in TRH-induced peak TSH responses was observed in euthyroid obese subjects of groups I and II, whereas hypothyroid subjects of group III showed only a slight decrement (<25%). CONCLUSIONS: The sensitivity of the TSH secretory system to glucocorticoid inhibitory action is preserved in obese subjects with abnormally elevated TSH response to TRH, but not in subclinically hypothyroid obese patients. The TRH plus dex test might be useful in future studies to understand the mechanisms underlying alterations in TSH secretion in obesity.

[Primary empty sella syndrome. Observations on 71 cases]. / Sindrome della sella turcica vuota primitiva. Osservazioni su 71 casi.

Primary empty sella syndrome (ESS) is an anatomo-radiological picture characterized by the presence of an arachnoid herniation filled with liquor that compresses the pituitary against the sellar wall. ESS occurs particularly in obese, hypertensive, cephalgic women, it is often asymptomatic but it may be associated with ophthalmologic, neurologic and sometime non-characterizing endocrine disorders. We report here 71 cases of primary ESS observed and assessed during the last fourteen years. The following endocrinological diagnostic procedures were carried out: hormonal (RIA) basal profile: FT3, FT4, TSH, PRL, ACTH, FSH, LH, 8.00 a.m. and p.m. cortisolemia, Aldo, PRA, DHEA-S, FTe, E2, P, PTH, CT, and calcemia and phosphoremia; provocative tests: TRH, GnRH, insulin hypoglycemia, etc.; inhibition tests: "overnight" and high dose dexamethasone. Clinical, radiological (skull radiographs, CT and/or MRI) and ophthalmologic (fundus, visual fields) assessment were made. We found principally cephalgia (52/71: 73.2%), hypertension (42/71: 59.1%), obesity (47/71: 66.1%). But we found especially mental disorders (57/71: 80.2%), in our knowledge not previously reported in the literature, as anxiety or dysthymic disorders with behavioural disturbances (chiefly oral compulsion). We found endocrinopathies in 36/71 (50.7%), isolated or coexisting in some patients: hyperPRL (14%), hypopituitarism (10.4%), hypogonadism (7%), diabetes insipidus (2.8%), hyperACTH (1.4%), hypoGH (15.4%), pituitary adenomas (8.4%). Several hypothalamic illness show a clinical picture including mental disorders and obesity. The Authors hypothesize that the ESS may be a "new" hypothalamic syndrome (compression/stretching on hypophysis and/or hypophyseal stalk by arachnoidocele; disorder of some hormones and neurotransmitters as leptin, neuropeptide Y, orexins, POMC-derived peptides, etc).

[Heart failure as clinical onset of essential mixed cryoglobulinemia]. / Scompenso cardiaco quale esordio clinico di crioglobulinemia mista essenziale.

The case of a 58-year old man affected by heart failure on ischemic basis, as clinical onset of essential mixed cryoglobulinemia (EMC) is reported. Laboratory assays, ECG at rest and exercise electrocardiogram, echocardiogram, myocardial scintigraphy, cardiac catheterization with coronarography, hepatic, bone and kidney biopsies confirmed the diagnosis. Cases of primitive heart involvement are rarely reported and are, usually, due to myocardial infarction. Nevertheless in the published series of cases, heart failure is often coupled with EMC and, not seldom, is the cause of death. In the present case heart failure was the dominant element of clinical symptomatology and wasn't consequent to renal involvement or hypertension, but was sustained by a myocardial contractile deficiency, on ischemic basis, with undamaged coronary circle at angiography. Therefore heart failure was ascribed to an involvement of coronary microcirculation in the course of systemic vasculitis.

Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen conssumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85 per cent of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.

Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri.

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85% of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.

On the role of actomyosin ATPases in regulation of ATP turnover rates during intense exercise.

Actomyosin ATPase is the dominant ATP sink during muscle work. Its catalytic capacities in fast-twitch oxidative glycolytic fibers have long been known to exceed by about 3-fold those of slow-twitch oxidative fibers, but the relative contributions to control of metabolic rates during exercise have never been closely examined. We compared fast-twitch oxidative glycolytic and slow-twitch oxidative fibers that displayed similar mitochondrial abundance (similar activities of mitochondrial marker enzymes). During short-term, but near maximum, aerobic exercise, fast-twitch oxidative glycolytic fibers displayed ATP turnover rates that were 2-4 times higher than for slow-twitch oxidative fibers (despite similar mitochondrial metabolic capacities), implying a large ATPase contribution to control of maximum metabolic rate. Fluxes through the ATP in equilibrium ADP + Pi cycle were extremely well regulated; at the lower limit, the forward flux exceeded the backward flux by only 0.06%, whereas at the upper limit, ATPase rates exceeded ATP synthesis rates by 0.12%. This very high precision of energy coupling could not be easily explained by standard metabolic regulation models.